1. Field of the Invention
The present invention relates to an ink supply device that supplies ink into a sub ink tank of a recording head unit, an ink-jet recording device having the ink supply device, and a method of supplying ink.
2. Description of the Related Art
In the ink-jet recording device that ejects ink drops on a recording medium such as a paper from recording heads on the basis of image information and records the image, there is such a configuration that mounts the sub ink tanks corresponding to each of the recording heads on a carriage to make the recording heads scan, in which there are various types of proposals as to the supply of ink into the sub ink tanks.
For example, Japanese Published Unexamined Patent Application No. Hei 6-238911 discloses an ink-jet printer as shown in FIG. 18, in which an ink tank 314 is disposed on one end of the shifting range of a recording head 312. The ink tank 314 has an ink supply outlet 318 formed at a position corresponding to an ink supply inlet 316 of the recording head 312, and has a bellow portion 320 formed on the middle thereof. And, as the recording head 312 returns to the home position, the ink supply inlet 316 of the recording head 312 is connected with the ink supply outlet 318 of the ink tank 314, and the recording head 312 is pressed to the ink tank 314 by a drive force of a drive motor not illustrated; thus, the bellow portion 320 of the ink tank 314 shrinks by this pressing force. Accordingly, the content volume of the ink tank 314 varies, and the ink inside the ink tank 314 flows into a common liquid chamber by way of the ink supply outlet 318 and the ink supply inlet 316. The ink tank 314 that once shrank recovers the original volume by the recording head 312 shifting and releasing the pressure, and by a self-restoring force of the bellow portion 320. AT this moment, a check valve 322 provided with the ink tank 314 opens, and the air equivalent to the volume of ink supplied into the recording head 312 flows into the ink tank 314 from an air intake 324.
However, in the construction in which the supply of ink is carried out by such pressurization, the supply of ink can take a comparably long time in some cases, which sometime lowers the efficiency of the ink supply.
In contrast to this, as shown in FIG. 19 and FIG. 20, the Japanese Published Unexamined Patent Application No. Hei 11-240180 discloses an ink-jet recording device that includes a first tank 354 provided with a recording head 352 and a second tank 356 to supply ink into the first tank 354. A switching hole 362 on a partition wall 360 that separates an ink chamber 358 of the first tank 354 from the recording head 352 can be opened and closed by a check valve 364; and as a differential pressure is produced, the switching hole 362 is to open. Supply of ink into the ink chamber 358 needs to couple a suction hole 366 with a suction cap 368, and thereafter drive a supply pump 370, thus decompressing the first tank 354. Next, a rubber seal 372 is made to advance by driving a reversible motor, and a needle 374 projected on the first tank 354 is inserted into the rubber seal 372, whereby the first tank 354 is connected with the second tank 356. Since the first tank 354 is in decompression, the ink is supplied from the second tank 356 into the first tank 354 by way of a tube 376.
However, in this construction, since the first tank 354 is not made to communicate with the atmosphere, the check valve 364 is required in order to prevent an ink leakage or air suction through a nozzle 378, due to a variation of the inner pressure, thereby making the structure complicated.